This invention relates generally to worm gear speed reducers and more particularly to a worm gear speed reducer in which the backlash between the worm and worm gear may be quickly adjusted and, when necessary, readjusted to near zero without having to remove the speed reducer out of service.
Worm gear speed reducers are often used in operations which require a high degree of precision and it is therefore necessary that zero or minimal backlash between the worm and worm gear of the reducer be maintained. Typical industrial applications include machine tools, indexing equipment, robotic positioners, rotary tables, servo positioning, all of which mandate precise power transmission between the worm and worm gear. Backlash may occur in a worm gear speed reducer at the time of initial assembly because of inaccurate machining and/or assembly operations or may develop in the reducer after use because of wear on the teeth of the worm gear or on the thread of the worm. Various proposals have been offered in attempting to eliminate the undesirable backlash and typical proposals are illustrated in U.S. Pat. Nos. 3,220,277, 3,463,030 and 4,261,218. However none of these proposals enables the backlash between the worm and the worm gear to be quickly eliminated by a convenient adjustment mechanism without taking the reducer unit out of service.